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Master's Dissertation
DOI
10.11606/D.21.2014.tde-17032015-162747
Document
Author
Full name
Gilberto Akio Oliveira Watanabe
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2014
Supervisor
Committee
Castro Filho, Belmiro Mendes de (President)
Cirano, Mauro
Harari, Joseph
Title in Portuguese
Marés internas semi-diurnas na plataforma continental amazônica
Keywords in Portuguese
AMASSedS
FOE
Marés Internas
Plataforma Continental Amazônica
Abstract in Portuguese
Ondas internas são movimentos ondulatórios que ocorrem no interior da coluna de água, associadas à estratificação de densidade. Ondas internas cuja frequência de oscilação se assemelha à das marés são chamadas marés internas. Estas ocasionam escoamentos intensos que influenciam a dinâmica de sedimentos, os processos de mistura e a produtividade primária. Em um ambiente energético como a Plataforma Continental Amazônica (PCA), localizada na costa norte brasileira, a estratificação varia consideravelmente, tanto espacial quanto temporalmente, de acordo com o balanço entre as diversas forçantes presentes. Na região da PCA alguns autores sugerem a presença de marés internas, entretanto, estudos específicos acerca do tema não figuram na literatura. Dessa forma, desenvolvemos neste trabalho um estudo da maré interna na região da PCA. Como objetivo, procuramos comprovar a ocorrência de marés internas na PCA, caracterizar seu comportamento e verificar sua intermitência. Para tal foram realizadas análises de dados provenientes do programa AMASSedS (A Multidisciplinary Amazon Shelf Sediment Study). Para caracterizar as marés internas, aplicamos dois métodos distintos para obtenção do campo baroclínico. O primeiro foi fundamentado no estabelecimento de uma corrente barotrópica préviamente obtida atráves de simulações numéricas. O segundo método empregado embasou-se na aplicação das funções empíricas ortogonais para a separação em modos estatísticos. Verificamos que as ondas internas na PCA estão ligadas à vazão do Rio Amazonas e são observadas, principalmente, na frequência semi-diurna. Aparentemente, as marés internas semi-diurnas influenciam não somente a hidrodinâmica da PCA como também são responsáveis por parte da variabilidade da salinidade próximo à superfície.
Title in English
Semidiurnal internal tides on the amazon continental shelf
Keywords in English
AMASSedS
Amazon Continental Shelf
EOF
Internal Tides
Abstract in English
Internal waves are oscillatory motions that occur within the density stratified ocean. The ones with tidal frequency are then called internal tides or baroclinic tides, and are, on several locations around the planet, responsible for strong fluxes that affect several processes, like sediment transport, mixing processes and primary production. In such a strong environment as the Amazon Continental Shelf (ACS), located at the northern brazilian coast, it's stratification changes considerably with time and space, accordingly with the balance between the several forcing variables present. In this region, some authors suggest that internal tides occur, however, none research have been made about it on the ACS. That being said, we propose a study on internal tides on the ACS. As we hypothesize that internal tides occur, we look forward to characterize it's behavior and verify it's intermittency on the ACS. To do so, the data collected during the AMASSedS project (A Multidisciplinary Amazon Shelf Sediment Study) is going to be analyzed. In order to characterize it, two different method were applied to obtain the baroclinic field. The first method was the definition of a modeled-based barotropic current of the ACS obtained on the literature. The second method was the application of Empirical Orthogonal Functions in order to split the field on statistical modes of variability and analyze them separately. Our results indicate that internal tides on the ACS occur preferentially on the semi-diurnal frequency and it's generation is intimately connected to river discharge. Also, the analysis of the salinity anomaly field indicates that internal tides are responsible for part of the variability of the later on the surface on mid-shelf.
 
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Publishing Date
2015-03-18
 
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